Template Names
For templates it is safest to only use alphanumeric characters and not use any special characters, only use a-z A-Z 0-9 and spaces. Normal dashes are ok but things like a long dash from Word are best avoided too.

Email Subject Lines
For email subject lines you can use special characters and emojis but not all email clients recognize them and they can also trigger spam filters - here is Emma's article about it.  
The general advice is they can be used, but do it sparingly and test across your main email clients.